Conventionally, the permanent magnet materials have been adopted for the rotor of generator in order to improve the efficiency. The strong point of the permanent magnet generator has high power in spite of low speed conditions because of having strong magnetic power. But, as the voltage of permanent magnet generator increases in proportion to revolution speed because of having constant magnetic force, the voltage raises too much at high speed conditions and it is very difficult to control the voltage constantly. However, recently the control of the voltage has been realized see, Japanese Patent Nos. 4463872, 4712896, and 4913424) by the simple control system which was invented by the inventor of this patent. As the result, reducing size of generator is required for next subject. Then it is very convenient technology.
For example, the smaller the size of generator is, the better ability of assemble is, then it is very convenient. Moreover, the demand of electric power is increasing very much therefore power up and down sizing are required more and more.
In addition, in the electro-magnetic generator which has been used for conventional vehicles, electro-magnetic force is generated by current flown in the rotor, and the electromotive force is produced in the winding of stator mounted on outer periphery of rotor and electric power is produced. However, the electric generator has a problem that it is very difficult to get high power at low speed condition because the magnetic power of the rotor is too low. Then they adopted a transmission in order to increase rotating speeds of generator and get high power at low speed condition. As increasing generator speed has been limited, then the generator size increases gradually. However, the increase of generator size is also limited and a shortage of generating power is very big problem for drivers because of experience battery die.
In addition, the permanent magnet generators for the vehicle have been studied to realize many times, however, the size of the generator became too large in order to get necessary power, and they have not succeeded in developing a generator with extreme small size, then, they have given up to install the permanent magnet generator into vehicles. However, recently IPMSM (Interior Permanent Magnet Synchronous Motor) generator which is made by soft magnetic material for the rotor and inserted permanent magnetic members, has been developed (see, Non patent literature Ohm-sha “Umekomi-jishaku doki-mota-no sekkei to seijyo (Design and control of Interior permanent magnet synchronous motor)” TAKEDA Yuji, et al.) and they have succeeded in to increase the torque at low speed condition. In this IPMSM, the electrical magnetic force is produced by a current and it is added to permanent magnetic force in the rotor produced by the soft magnetic material. As the results, the magnetic force summed up the electric and permanent magnet force increase large and the system is used for the synchronous motor in the hybrid vehicle because the systems have the specific characteristics of the high efficiency, compact size and light weight compared with a conventional induction motor. The IPMSM can be used for generator.